Methods of forming capacitors and methods of forming capacitor dielectric layers

ABSTRACT

A method of forming a capacitor includes forming first capacitor electrode material over a semiconductor substrate. A silicon nitride comprising layer is formed over the first capacitor electrode material. The semiconductor substrate with silicon nitride comprising layer is provided within a chamber. An oxygen comprising plasma is generated remote from the chamber. The remote plasma generated oxygen is fed to the semiconductor substrate within the chamber at a substrate temperature of no greater than 750° C. effective to form a silicon oxide comprising layer over the silicon nitride comprising layer. After the feeding, a second capacitor electrode material is formed over the silicon oxide comprising layer. Methods of forming capacitor dielectric layers are also disclosed.

TECHNICAL FIELD

[0001] This invention relates to methods of forming capacitors and tomethods of forming capacitor dielectric layers.

BACKGROUND OF THE INVENTION

[0002] Capacitors are commonly-used electrical components insemiconductor circuitry, for example in DRAM circuitry. As integratedcircuitry density increases, there is a continuing challenge to maintainsufficiently high storage capacitance despite decreasing capacitor area.A typical capacitor is comprised of two conductive electrodes separatedby a non-conducting dielectric region. The dielectric region ispreferably comprised of one or more materials preferably having a highdielectric constant and low leakage current characteristics. Examplematerials include silicon compounds, such as SiO₂, and Si₃N₄. Si₃N₄ istypically preferred due to its higher dielectric constant than SiO₂.

[0003] Numerous capacitor dielectric materials have been and are beingdeveloped in an effort to meet the increasing stringent requirementsassociated with the production of smaller and smaller capacitor devicesused in higher density integrated circuitry. Most of these materials do,however, add increased process complexity or cost over utilization ofconventional SiO₂ and Si₃N₄ capacitor dielectric materials.

[0004] One dielectric region in use today includes a composite ofsilicon oxide and silicon nitride layers. Specifically, a firstcapacitor electrode is formed to have a silicon oxide comprising layer,typically silicon dioxide, of 6 to 10 Angstroms thereover. Such might beformed by deposition, or more typically by ambient or native oxideformation due to oxidation of the first electrode material (for exampleconductively doped polysilicon) when exposed to clean room ambientatmosphere. Thereafter, a silicon nitride layer is typically depositedby low pressure chemical vapor deposition. This can, however,undesirably produce very small pinholes in the silicon nitride layer,particularly with thin layers of less than 200 Angstroms, with thepinholes becoming particularly problematic in layers of less than orequal to about 75 Angstroms thick. These pinholes can undesirably reducefilm density and result in undesired leakage current in operation.

[0005] One technique for filling such pinholes is to wet oxidize thesubstrate, for example at 750° C.-800° C., atmospheric pressure, andfeeding 5 slpm H₂, 10 slpm O₂ for 15-60 minutes. Such forms siliconoxide material which fills the pinholes and forms a silicon oxide layertypically from about 5 Angstroms to about 25 Angstroms thick over thesilicon nitride. It is generally desirable, however, to overall minimizethe thermal exposure of the wafer/substrate upon which integratedcircuitry is being fabricated. Exposure to 750° C.-800° C. for from 15minutes-60 minutes is significant in this regard.

SUMMARY

[0006] The invention includes methods of forming capacitors and methodsof forming capacitor dielectric layers. In one implementation, a methodof forming a capacitor dielectric layer includes forming a siliconnitride comprising layer over a substrate. The substrate with siliconnitride comprising layer is provided within a chamber. An oxygencomprising plasma is generated remote from the chamber. The remoteplasma generated oxygen is fed to the substrate within the chamber at asubstrate temperature of no greater than 750° C. effective to form asilicon oxide comprising layer over the silicon nitride comprisinglayer.

[0007] In one implementation, a method of forming a capacitor includesforming first capacitor electrode material comprising silicon over asemiconductor substrate. A silicon nitride comprising layer is formedover the first capacitor electrode material. The silicon nitridecomprising layer has pinholes formed therein. The semiconductorsubstrate with silicon nitride comprising layer is provided within achamber. An oxygen comprising plasma is generated remote from thechamber. The remote plasma generated oxygen is fed to the semiconductorsubstrate within the chamber at a substrate temperature of no greaterthan 550° C. and for no longer than 30 seconds effective to form asilicon oxide comprising layer over the silicon nitride comprising layerand effective to fill said pinholes with silicon oxide. The chamber isessentially void of hydrogen during the feeding. After the feeding, asecond capacitor electrode material is formed over the silicon oxidecomprising layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0009]FIG. 1 is a diagrammatic sectional view of a semiconductor waferfragment in process in accordance with an aspect of the invention.

[0010]FIG. 2 is a diagrammatic view of processing equipment.

[0011]FIG. 3 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that shown by FIG. 1.

[0012]FIG. 4 is a view of the FIG. 3 wafer fragment at a processing stepsubsequent to that shown by FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0014] Referring initially to FIG. 1, a wafer fragment in process inaccordance with a method of forming a capacitor in accordance with anaspect of the invention is indicated generally with reference numeral10. Such comprises a bulk monocrystalline silicon substrate 12. In thecontext of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove. Also in the context of this document, the term “layer” includesboth the plural and the singular unless otherwise indicated. Aninsulative layer 14, for example doped or undoped silicon dioxide, orsilicon nitride, is formed over bulk substrate 12.

[0015] A first capacitor electrode material 16 is formed over insulativelayer 14. At this point, or preferably later in the process, electrodematerial 16 is ultimately patterned/provided into some desired firstcapacitor electrode shape. Exemplary materials for electrode 16 includesilicon (for example polysilicon) metals, conductive metal oxides, andany other conductive layer. An exemplary thickness in one preferredembodiment, and particularly where layer 16 comprises polysilicon, is600 Angstroms. A first or inner silicon oxide comprising layer 18 isformed over, and “on” as shown, first capacitor electrode 16. Anexemplary method for forming layer 18 is by oxidizing an outer portionof electrode material 16, for example by exposure to clean room ambient.This oxide layer is not preferred, but rather an effect of an exposedsilicon or other oxidizable substrate. Typical thickness for layer 18 isless than or equal to 15 Angstroms. Layer 18 preferably consistsessentially of silicon dioxide.

[0016] A silicon nitride comprising layer 20 is formed over firstcapacitor electrode material 16 and in the illustrated preferredembodiment is formed on first or inner silicon oxide comprising layer18. An exemplary thickness is from 30 Angstroms to 80 Angstroms. In butone embodiment, silicon nitride comprising layer 20 is formed to have aplurality of pinholes 22 formed therein. Such are shown in exaggeratedwidth/size in the figures for clarity. In the illustrated embodiment, atleast some pinholes extend completely through layer 20 to silicon oxidecomprising layer 18. Silicon nitride comprising layer 20 might bedeposited by any existing or yet-to-be developed technique, withchemical vapor deposition or plasma enhanced chemical vapor depositionbeing but examples. One exemplary process whereby a silicon nitridelayer 20 is deposited by chemical vapor deposition includes NH₃ at 300sccm, dichlorosilane at 100 sccm, 750 mTorr, 600° C., and 60 minutes ofprocessing.

[0017] Referring to FIG. 2, semiconductor substrate 10 with siliconnitride comprising layer 20 is provided within a processing chamber 60.The processing chamber might be the same or different from any chamberutilized to produce any of the FIG. 1 construction. An example preferredprocessing chamber is a rapid thermal processor, with the inventionbeing reduced to practice using an Applied Materials RTP-XE Chamberhaving a volume of 2700 cc. A suitable remote plasma generator 62 isdiagrammatically shown and provided upstream of processing chamber 60.Any suitable remote plasma generation is contemplated, whether existingor yet-to-be-developed, with by way of example only microwave and RFplasma generation being examples. The invention was reduced to practiceusing an ASTEX F120160-02 power source with a microwave unit numberAx3151-1, available from ASTEX of Wilmington, Mass. FIG. 2 depicts asuitable oxygen gas feed and an inert gas feed to the diagrammaticremote plasma generator 62.

[0018] An oxygen comprising plasma is generated remote from chamber 60,for example in generator 62. The remote plasma generated oxygen is thenfed to the semiconductor substrate within chamber 60, with the substratetemperature being no greater than 750° C., effective to form a siliconoxide comprising layer 24 (FIG. 3) over, preferably “on” as shown,silicon nitride comprising layer 20, and effective to fill pinholes 22with silicon oxide. More preferably, the substrate temperature duringthe feeding is maintained at no greater than 550° C., and even morepreferably no greater than 500° C. Further preferably, the feeding isfor no longer than 1 minute, with a feeding of less than or equal to 30seconds being more preferred, and a feeding of less than or equal to 15seconds being most preferred. In the most preferred embodiment, layers18, 20 and 24 constitute a dielectric region 27 of the capacitor beingformed, with such dielectric region consisting essentially of an ONOcomposite which consists essentially of such silicon oxidecomprising-silicon nitride comprising silicon oxide comprising layers.

[0019] The oxygen comprising plasma is preferably derived, at least inpart, from a gas selected from the group consisting of O₂, O₃,N_(y)O_(x) (with “x” and “y” being greater than zero) and mixturesthereof. Further as shown in the FIG. 2 embodiment, the oxygencomprising plasma is preferably generated, at least in part, from asuitable inert gas in addition to an oxygen feed gas. Examples includeN₂, Ar and He. One specific example includes an oxygen comprising plasmaderived, at least in part, from feeding O₂ and N₂. Another exemplaryembodiment in accordance with the above parameters includes forming anoxygen comprising plasma derived, at least in part, from N₂O and atleast one of Ar and He. Preferably in such latter example, the ultimatefeeding of the remote generated plasma material to chamber 60 is void offeeding of N₂ but for N₂ which is inherently produced from thedissociation of N₂O in the generation of the remote plasma. Furtherpreferably, and contrary to the prior art described above, chamber 60 isessentially void of hydrogen during the feeding, thereby preventing anysteam formation. In the context of this document, “essentially void”means below detectable levels.

[0020] A specific example with respect to the FIG. 2 processing with theASTEX and Applied Materials equipments includes a feed of 2000 sccm withO₂ and 1000 sccm of N₂. Pressure within the remote plasma unit wasmaintained at approximately 2.9 Torr with microwave power provided at2000 Watts. Temperature of the wafer was 650° C., with pressuremaintained at 2.9 Torr. By way of example only, and with respect to theabove-identified reduction-to-practice equipment, pressure is preferablymaintained within the system at from 1 to 8 Torr, power supplied to theremote plasma generator at from 500 Watts to 3000 Watts, and temperaturemaintained within the system at from 500° C. to 750° C. Preferred flowranges for each of O₂ and N₂ are from 0.5 slm to 5 slm. Temperatures aslow as 350° C. might be used with other equipment.

[0021] The above-described preferred embodiments, in the fabrication ofa capacitor dielectric region such as region 27, reduces the thermalexposure as compared to the prior art, in the most preferred embodiment,from in excess of 750° C. to less than 550° C., and further with thepreferred embodiment reducing the exposure time even at the reducedtemperature to well less than 1 minute. Properties of the capacitordielectric region formed as described above appear comparable to ONOlayers produced by prior art methods. For example, exposure of thedielectric region nitride to a remote oxygen plasma at 2000 Watts for 10seconds resulted in a capacitor dielectric region having capacitance andleakage approximately equivalent to a prior art control wet oxidation.Further, an improvement in breakdown voltage for the 2000 Watt, 10second treatment indicates that an increased capacitance via reducedthickness might be feasible, also.

[0022] Referring to FIG. 4, and after the feeding, a second capacitorelectrode material 40 is formed over silicon oxide comprising layer 24.In the preferred and illustrated embodiment, second capacitor electrodematerial 40 is formed on (in contact with) oxide layer 24. An exemplarythickness for layer 40 is from 300 Angstroms to 600 Angstroms. Secondelectrode material 40 might comprise the same or different materialsfrom first electrode material 16.

[0023] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a capacitor comprising: forming first capacitorelectrode material over a semiconductor substrate; forming a siliconnitride comprising layer over the first capacitor electrode material;providing the semiconductor substrate with silicon nitride comprisinglayer within a chamber; generating an oxygen comprising plasma remotefrom the chamber; feeding the remote plasma generated oxygen to thesemiconductor substrate within the chamber at a substrate temperature ofno greater than 750° C. effective to form a silicon oxide comprisinglayer over the silicon nitride comprising layer; and after the feeding,forming second capacitor electrode material over the silicon oxidecomprising layer.
 2. The method of claim 1 wherein the substratetemperature during the feeding is no greater than 550° C.
 3. The methodof claim 1 wherein the substrate temperature during the feeding is nogreater than 500° C.
 4. The method of claim 1 wherein the chambercomprises a rapid thermal processing chamber.
 5. The method of claim 1wherein the feeding is for no longer than 1 minute.
 6. The method ofclaim 1 wherein the feeding is for no longer than 30 seconds.
 7. Themethod of claim 1 wherein the feeding is for no longer than 15 seconds.8. The method of claim 1 wherein the chamber is essentially void ofhydrogen during the feeding.
 9. The method of claim 1 wherein the oxygencomprising plasma is at least in part derived from a gas selected fromthe group consisting of O₂, O₃, N_(y)O_(x), and mixtures thereof. 10.The method of claim 9 wherein the oxygen comprising plasma is at leastin part generated from an inert gas.
 11. The method of claim 1 whereinthe oxygen comprising plasma is at least in part derived from O₂ and N₂.12. The method of claim 1 wherein the oxygen comprising plasma is atleast in part derived from N₂O and at least one of Ar and He.
 13. Themethod of claim 1 wherein the oxygen comprising plasma is at least inpart derived from N₂O and at least one of Ar and He, the feeding beingvoid of feeding of N₂ but for N₂ produced from dissociation of N₂O inthe remote generated plasma.
 14. A method of forming a capacitorcomprising: forming first capacitor electrode material over asemiconductor substrate; forming a silicon nitride comprising layer overthe first capacitor electrode material; providing the semiconductorsubstrate with silicon nitride comprising layer within a chamber;generating an oxygen comprising plasma remote from the chamber; feedingthe remote plasma generated oxygen to the semiconductor substrate withinthe chamber at a substrate temperature of no greater than 550° C. andfor no longer than 30 seconds effective to form a silicon oxidecomprising layer over the silicon nitride comprising layer; and afterthe feeding, forming second capacitor electrode material over thesilicon oxide comprising layer.
 15. The method of claim 14 wherein thesubstrate temperature during the feeding is no greater than 500° C. 16.The method of claim 14 further comprising forming a silicon oxidecomprising layer over the first capacitor electrode material prior toforming the silicon nitride comprising layer, the capacitor being formedto have a dielectric region consisting essentially of an ONO compositeconsisting essentially of said silicon oxide comprising layer and saidsilicon nitride comprising layer.
 17. The method of claim 14 wherein thefeeding is for no longer than 15 seconds.
 18. The method of claim 14wherein the chamber is essentially void of hydrogen during the feeding.19. The method of claim 14 wherein the oxygen comprising plasma is atleast in part derived from a gas selected from the group consisting ofO₂, O₃, N_(y)O_(x), and mixtures thereof.
 20. The method of claim 19wherein the oxygen comprising plasma is at least in part generated froman inert gas.
 21. The method of claim 14 wherein the oxygen comprisingplasma is at least in part derived from O₂ and N₂.
 22. The method ofclaim 14 wherein the oxygen comprising plasma is at least in partderived from N₂O and at least one of Ar and He.
 23. The method of claim14 wherein the oxygen comprising plasma is at least in part derived fromN₂O and at least one of Ar and He, the feeding being void of feeding ofN₂ but for N₂ produced from dissociation of N₂ 0 in the remote generatedplasma.
 24. A method of forming a capacitor comprising: forming firstcapacitor electrode material comprising silicon over a semiconductorsubstrate; forming a silicon nitride comprising layer over the firstcapacitor electrode material, the silicon nitride comprising layercomprising pinholes formed therein; providing the semiconductorsubstrate with silicon nitride comprising layer within a chamber;generating an oxygen comprising plasma remote from the chamber; feedingthe remote plasma generated oxygen to the semiconductor substrate withinthe chamber at a substrate temperature of no greater than 550° C. andfor no longer than 30 seconds effective to form a silicon oxidecomprising layer over the silicon nitride comprising layer and effectiveto fill said pinholes with silicon oxide, the chamber being essentiallyvoid of hydrogen during the feeding; and after the feeding, formingsecond capacitor electrode material over the silicon oxide comprisinglayer.
 25. The method of claim 24 wherein the substrate temperatureduring the feeding is no greater than 500° C.
 26. The method of claim 24further comprising forming a silicon oxide comprising layer over thefirst capacitor electrode material prior to forming the silicon nitridecomprising layer, the capacitor being formed to have a dielectric regionconsisting essentially of an ONO composite consisting essentially ofsaid silicon oxide comprising layer and said silicon nitride comprisinglayer.
 27. The method of claim 24 wherein the feeding is for no longerthan 15 seconds.
 28. The method of claim 24 wherein the oxygencomprising plasma is at least in part derived from a gas selected fromthe group consisting of O₂, O₃, N_(y)O_(x), and mixtures thereof. 29.The method of claim 28 wherein the oxygen comprising plasma is at leastin part generated from an inert gas.
 30. The method of claim 24 whereinthe oxygen comprising plasma is at least in part derived from O₂ and N₂.31. The method of claim 24 wherein the oxygen comprising plasma is atleast in part derived from N₂O and at least one of Ar and He.
 32. Themethod of claim 24 wherein the oxygen comprising plasma is at least inpart derived from N₂O and at least one of Ar and He, the feeding beingvoid of feeding of N₂ but for N₂ produced from dissociation of N₂O inthe remote generated plasma.
 33. A method of forming a capacitordielectric layer, comprising: forming a silicon nitride comprising layerover a substrate; providing the substrate with silicon nitridecomprising layer within a chamber; generating an oxygen comprisingplasma remote from the chamber; and feeding the remote plasma generatedoxygen to the substrate within the chamber at a substrate temperature ofno greater than 750° C. effective to form a silicon oxide comprisinglayer over the silicon nitride comprising layer.
 34. The method of claim33 wherein the chamber comprises a rapid thermal processing chamber. 35.The method of claim 33 wherein the substrate temperature during thefeeding is no greater than 550° C.
 36. The method of claim 33 whereinthe substrate temperature during the feeding is no greater than 500° C.37. The method of claim 33 wherein the feeding is for no longer than 1minute.
 38. The method of claim 33 wherein the feeding is for no longerthan 30 seconds.
 39. The method of claim 33 wherein the feeding is forno longer than 15 seconds.
 40. The method of claim 33 wherein thechamber is essentially void of hydrogen during the feeding.
 41. Themethod of claim 33 wherein the oxygen comprising plasma is at least inpart derived from a gas selected from the group consisting of O₂, O₃,N_(y)O_(x), and mixtures thereof.
 42. The method of claim 41 wherein theoxygen comprising plasma is at least in part generated from an inertgas.
 43. The method of claim 33 wherein the oxygen comprising plasma isat least in part derived from O₂ and N₂.
 44. The method of claim 33wherein the oxygen comprising plasma is at least in part derived fromN₂O and at least one of Ar and He.
 45. The method of claim 33 whereinthe oxygen comprising plasma is at least in part derived from N₂O and atleast one of Ar and He, the feeding being void of feeding of N₂ but forN₂ produced from dissociation of N₂O in the remote generated plasma. 46.The method of claim 33 further comprising forming a silicon oxidecomprising layer over the first capacitor electrode material prior toforming the silicon nitride comprising layer, the capacitor being formedto have a dielectric region consisting essentially of an ONO compositeconsisting essentially of said silicon oxide comprising layer and saidsilicon nitride comprising layer.